Eyepieces used in binoculars, telescopes, microscopes, or other such optical devices are used as an optical system for enlarging a real image formed by an objective in order for the image to be viewed.
An important attribute relating to the performance of an eyepiece system is a large angle of field, but increasing the angle of field makes the eyepiece system susceptible to lateral chromatic aberration and various other aberrations, and correcting such aberrations is a serious problem.
Diffraction optical elements that differ significantly in configuration from a conventional optical lens have recently been used for such purposes as reducing these various aberrations in a variety of optical systems. Lens systems that use diffraction optical elements to minimize various aberrations, particularly lateral chromatic aberration, have been proposed in eyepiece systems as well (see, e.g., Patent Document 1).
Patent Document 1: U.S. Pat. No. 6,130,785